الفهرس 
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Abstract
Due to the increase in prices and taxes of conventional energy sources, a big gap in energy production and consumption is generated. On the other hand, the increment necessitates of fossil fuel creates and maximize this energy gap in Egypt. So the creation of local and alternative source of energy production has a high energy value instead of fossil fuel is needed. Huge quantities of and cattle manure are thrown on land and the misuse and dispose of these dairy processing wastes in a non-economic way without any management during the manufacture of cheese. It is necessary to process and recycle these wastes in order to increase the added value by anaerobic digestion technique for biogas production. The experiments were conducted from January to April 2021. The objectives of the present research may be mentioned as follows: The main objective of this study is to utilize the anaerobic fermentation technique for two potent pollutant waste materials (milk whey and cattle dung) for producing of value-added product; biogas and bio-fertilizer. The specific objectives of this study are to:- 1. Study the thermal performance analysis of complete solar heating system. 2. Determine the thermal performance of two identical digesters, one horizontally situated and the other is vertically located. 3. Investigate the effect of two different stirring speeds (60 and 120 rpm) for two different stirring times (5 and 15 minutes each hour). 4. Study the effect of two different wastes (mix of milk whey with cattle dung and mix of cattle dung with water) on the biogas production rate. 5. Determine the ratio of methane in the produced biogas from each treatment and assessed the heating values of biogas. 6. Using of an environmentally friendly product and application within the food and dairy industries or remote areas of Egypt. The Main experiment Agricultural wastes Cattle dung was taken from fattening cattle farm and whey used in this study was obtained from Local dairy factory, Governorate located in Tanta district, Gharbia governorate. All the wastes were taken fresh and conveyed immediately to Faculty of Agriculture of Tanta University. The cattle dung was diluted with water and whey to a final total solid (T.S) of 10% the required amount of whey to adjust the total solid in biogas digester at 10% for producing biogas at mesophilic conditions (37± 0.2°C) at a pH from 6.5 to 7.5. Digester Digester consists of galvanized steel sheet conduit of 0.4m in diameter, 0.8m in height and 0.0015m in thickness and a thermostatic heating unit was attached to the digester with a pump to regulate the temperature of the digester (37 ±0.2°C) via a control panel. Stirrer motor powered DC, fixed on the opposite side at the center of the digester and Digester is fully isolated from the outside with glasswool. The digester is connected to water displacement to measure volume of biogas generated from digestion process. Flat-plate solar collector The solar collector with insulation frame (1.8 x 2.49m) consists of cover plate of ordinary transparent glass of 6mm in thick, a heat absorbent dark colored plate is placed inside and inner copper pipes through which the water to be heated. The product of heated water is forced with a constant flow rate to the digester by a pump. B-Conclusions In general, biogas production from organic wastes as an alternative source of energy requires the adequate temperatures, especially during colder months. In the case of relying on electricity to heat the mixture, large amounts of energy are consumed during the experiment. However, solar energy as an alternative renewable energy contributes to reducing the consumption of electricity for heating the mixture inside the digesters. On the other hand, it cannot be completely relied upon to run the system all the time, especially during the night. Moreover, the use of whey in digestion processes to maximize the use of it and obtain a value-added product, knowing that whey was used in the production of biogas due to the little information in the literature on it, which is the motivation for conducting this study. Thus, two digester units were fabricated, solar energy system and a control unit to adjust the suitable conditions in the experiment. This current study was conducted in order to design two biogas production units with a solar energy system Plus evaluate its thermal performance, and thermal behavior of digestion, under experimental conditions. The obtained results of the experimental work could be summarized and determined as follows: 1- Biogas is a clean and renewable biofuel created from anaerobic biodegradation of organic matter, Local prospective technologies can be used to produce clean energy in the form of biogas and therefore improving and relying on them in Egypt will reduce the total dependence on fossil fuel sources, because it is low-capital and environmentally friendly compared to fossil fuel sources. 2- Utilization of biogas prevents harmful diseases and also reduces global warming. from a zero waste value lot of energy and income is generated. The flat- plate solar collector tilt angles had an important effect on the thermal performance and efficiency. 4- The maximum average value of thermal and absorption efficiency of flat plate solar collector obtained is 62.665% and 81.3% at optimum tilt angle is 21.58°and April. 5- General, the solar power system provided 74.4% of the energy consumed for heating the mixture at the digester during the experiment. 6- The nearer the pH is to the neutral mean of 7, increases the production of biogas and The minima cumulative biogas production of cattle dung with whey and cattle dung with water mixture are 29.8L at pH 6.98 and 25.6L at pH 6.85. 7- As adding whey with cattle dung led to an increase in methane production by 8.5% approximately with a biological conversion efficiency of 88%, compared to mixture cattle dung with water. 8- Mixing whey, which is an organic by-product, with cattle dung greatly contributed to converting the organic mixture to biogas and increasing production rate compared to cattle dung only. 9- The bioconversion efficiency of cattle dung with whey mixture ranged between 27.46 and 34.93% for all treatments, with the exclusion of a higher efficiency of 78.27% at a mixing speed of 60rpm and a stirring period of 5 minutes. 10- To promote homogeneity during the digestive process, stirring is essential. Furthermore, excessive stirring loses energy and may have a detrimental effect on reactor performance and methane generation. 11- The results obtained from the gas analysis, showed that cattle with whey contains a higher percentage of methane than the cattle with water, and it also produces faster and more gas in the same period during the anaerobic digestion process.